A number of conventional platforms exist for the collection of two-dimensional image data of the surface of a subject (or object) and using that two-dimensional data to render (or otherwise represent) the object as a three dimensional computer model. The majority of these systems use electromagnetic radiation in the form of visible wavelengths to illuminate the surface of the object so that the reflections can then be received by an appropriate sensor or camera and placed into electrical format. These platforms have sophisticated hardware and software that process the received information in a fashion where the collected two-dimensional information can be used to render the three dimensional model.
A feature which has proved useful in accurately recognizing the surface of the object to be imaged is the application of reference markers to the object's surface. These reference markers are typically both reflective and opaque, and provide a high degree of contrast with the surroundings, enabling them to serve as reliable position indicators for the imaging optics.
An application for these platforms is the imaging of human teeth, such as for dentistry and orthodontics. A hand-held scanner is brought into proximity with the teeth, illuminates them, captures the reflected light, and sends that information to the processing segment, which can then use it to generate a three-dimensional model of part of a tooth, an entire tooth, or multiple teeth, etc. Crowns, orthodontics, molds, and the like can then be generated from the model. However, the human tooth is translucent and can vary in color, and its surface features are not always readily distinguishable by the imaging optics. It is therefore difficult to assess the surface features and an accurate location of the tooth exterior without the aid of the aforementioned reference markers.
The attempts to apply reference markers to the teeth described in prior publications are either insufficient or come with significant limitations. For instance, the composition disclosed in Intl. Publication No. WO 2009/150596 (Ernst) is in reality a bi-layer approach that requires application of a reference marker composition in two steps. A glue-type layer is applied first, and this is followed by the application of the reference markers in powdered form. The application of a composition bearing reference markers can be hindered if it does not dry fast enough. The patient can accidentally remove the composition with his or her tongue or saliva while it is applied or before the teeth have been fully imaged. Also, if the composition remains in liquid form long enough, the powder can run off or settle in an uneven manner across the tooth's surface (e.g., into crevices) resulting in reference markers being disproportionately allocated and hindering the creation of a dense, evenly distributed pattern. To combat this, Ernst uses a third, drying step in between application of the glue and the powder. A multiple step application process is time consuming and relatively more complex.
Intl. Publication No. WO 2011/162965 (Johnson) addresses the problem of slow drying compositions by applying a contrast composition that varies in viscosity based on changes in temperature. The composition is described as having low viscosity at ambient temperature and higher viscosity at body temperature, such that when the composition heats after application to the teeth it acts more like a gel and less like a liquid. However, a highly viscous composition tends to be thick when applied to the teeth. This can be problematic for the imaging system which must compensate for thickness of the composition to determine where the actual tooth surface lies. Also, because the composition does not fully dry, there remains a risk that it will rub or run off.
Intl. Publication No. WO 2011/056574 (Hall-Holt) recognizes the desirability of applying reference markers to teeth but does not describe the enabling specifics of a composition that can be used to apply those markers in practice. Hall-Holt suggests compositions that have a high viscosity, but does not disclose compositions that dry rapidly.
Intl. Publication No. WO 03/077839 (Butcher) discloses a composition that is predominantly alcohol and also uses a denture adhesive as a binding agent. Because of the high alcohol content (40%-94% by weight), this composition can potentially cause discomfort to a patient because of the thermal transfer that occurs during the evaporation of such a high alcohol content. This can be particularly troublesome with patients that have “cold-sensitive” teeth. Also, such a large alcohol content will typically take upwards of several minutes to dry.
New compositions and methods of their use are therefore needed to address these and other deficiencies in the current state of the art.